People are generally aware of the most common causes of hallucinations, like schizophrenia and a really high fever. But lesser known are the more rare causes; here are six you probably haven't heard about.

Health authorities said on Thursday that more people than previously thought received possibly tainted steroid injections and that some 14,000 patients could be at risk of contracting meningitis in an unprecedented outbreak of the disease.

The Centers for Disease Control and Prevention said the number of people at risk, which is 1,000 higher than earlier estimated, was revised after consulting with health authorities.

Fourteen patients have died from meningitis and 170 people have been infected, the CDC said in its latest update on Thursday. The number of infections rose by 33 since Wednesday, the CDC said.

Florida reported a second death from meningitis and Indiana reported its first death from the outbreak. Meningitis cases have been confirmed in 11 states.

The health scare prompted U.S. Senator Richard Blumenthal, who sits on the Senate's health oversight committee, to ask federal authorities to probe whether a Massachusetts specialty pharmacy that produced the steroid misled regulators about its operations.

The outbreak has developed into a major health scandal, with authorities scrambling to determine how vials of a steroid used mainly to treat back pain were contaminated, track down those affected and treat them. It has also raised questions about how the pharmaceuticals industry operates and is regulated.

Blumenthal, a former Connecticut state attorney general and federal prosecutor, said he had reached no conclusions but that an investigation was warranted.

"The company, its officers, employees and maybe others may have violated state and federal criminal laws in their potential misrepresentations to government agencies regarding their products," Blumenthal told Reuters in a telephone interview.

Blumenthal said he submitted his request for a federal criminal probe in a letter to U.S. Attorney General Eric Holder.

"The fact that death and serious injuries resulted from the potential violations of law certainly is relevant, and the misstatements or fraud could constitute a violation of federal mail and wire fraud prohibitions," Blumenthal said.

Lawmakers have come under pressure to close what critics see as a loophole in oversight that left the New England Compounding Company, or NECC, the Massachusetts pharmacy linked to the tainted steroids, largely exempt from federal regulation.

PROBE BY STATE AND FEDERAL OFFICIALS

The U.S. Food and Drug Administration regulates only the ingredients and their suppliers, not the little-known corner of the drug world known as "compounding," which is subject to a patchwork of state oversight.

State and federal officials are now investigating NECC, which distributed thousands of vials of a contaminated steroid made at a shabby brick complex next to a waste and recycling operation in a western suburb of Boston. The company has suspended operations and recalled all of its products.

The pharmacies are owned by Gregory Conigliaro, an engineer, and his brother-in-law Barry Cadden, a pharmacist who was in charge of pharmacy operations at NECC. The waste and recycling facility is another of Conigliaro's business interests.

Compounding pharmacies such as NECC are permitted to make medications based on specific prescriptions for individual patients.

State and federal regulators are investigating why NECC shipped thousands of vials of preservative-free methylprednisolone acetate steroid to healthcare facilities in multiple states.

"It does seem like the agencies, both at the state and the federal level, may have been misled by some of the information we were given," Massachusetts Governor Deval Patrick told reporters on Wednesday.

The number of cases has grown rapidly as health practitioners contacted about 13,000 people who received injections from a potentially tainted supply of steroid medication shipped to 23 states.

In six states - Tennessee, Michigan, Maryland, Virginia, Florida and now Indiana - the outbreak has claimed lives.

Five new cases were reported in Tennessee, which remained the hardest-hit state with 49 cases, the CDC said. Michigan added 11 cases and was at 39 on Thursday, with Virginia adding three to reach 30 and Indiana six to reach 21, the CDC said.

The other states reporting cases are Maryland (13), Florida (7), Ohio (3), Minnesota (3), New Jersey (2), North Carolina (2) and Idaho (1), the CDC said.

Thousands of people received the injections to relieve back pain and other complaints and are at risk of infection.

Meningitis is an infection of the membranes covering the brain and spinal cord. Symptoms include headache, fever and nausea. Fungal meningitis, unlike viral and bacterial meningitis, is not contagious.